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dist: expand functionality of the dist tool

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With this change, we add the following commands to the dist tool:

- `ingest`: verify and accept content into storage
- `active`: display active ingest processes
- `list`: list content in storage
- `path`: provide a path to a blob by digest
- `delete`: remove a piece of content from storage

We demonstrate the utility with the following shell pipeline:

```
$ ./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json | \
    jq -r '.layers[] | "./dist fetch docker.io/library/redis "+.digest + "| ./dist ingest --expected-digest "+.digest+" --expected-size "+(.size | tostring) +" docker.io/library/redis@"+.digest' | xargs -I{} -P10 -n1 sh -c "{}"
```

The above fetches a manifest, pipes it to jq, which assembles a shell
pipeline to ingest each layer into the content store. Because the
transactions are keyed by their digest, concurrent downloads and
downloads of repeated content are ignored. Each process is then executed
parallel using xargs.

Put shortly, this is a parallel layer download.

In a separate shell session, could monitor the active downloads with the
following:

```
$ watch -n0.2 ./dist active
```

For now, the content is downloaded into `.content` in the current
working directory. To watch the contents of this directory, you can use
the following:

```
$ watch -n0.2 tree .content
```

This will help to understand what is going on internally.

To get access to the layers, you can use the path command:

```
$./dist path sha256:010c454d55e53059beaba4044116ea4636f8dd8181e975d893931c7e7204fffa
sha256:010c454d55e53059beaba4044116ea4636f8dd8181e975d893931c7e7204fffa /home/sjd/go/src/github.com/docker/containerd/.content/blobs/sha256/010c454d55e53059beaba4044116ea4636f8dd8181e975d893931c7e7204fffa
```

When you are done, you can clear out the content with the classic xargs
pipeline:

```
$ ./dist list -q | xargs ./dist delete
```

Note that this is mostly a POC. Things like failed downloads and
abandoned download cleanup aren't quite handled. We'll probably make
adjustments around how content store transactions are handled to address
this.

From here, we'll build out full image pull and create tooling to get
runtime bundles from the fetched content.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
This commit is contained in:
Stephen J Day 2017-01-26 14:08:56 -08:00
parent 3c44ec5dbc
commit f9cd9be61a
No known key found for this signature in database
GPG key ID: 67B3DED84EDC823F
10 changed files with 532 additions and 36 deletions
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68
cmd/dist/active.go vendored Normal file
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@ -0,0 +1,68 @@
package main
import (
"fmt"
"os"
"path/filepath"
"text/tabwriter"
"time"
"github.com/docker/containerd/content"
units "github.com/docker/go-units"
"github.com/urfave/cli"
)
var activeCommand = cli.Command{
Name: "active",
Usage: "display active transfers.",
ArgsUsage: "[flags] [<key>, ...]",
Description: `Display the ongoing transfers.`,
Flags: []cli.Flag{
cli.DurationFlag{
Name: "timeout, t",
Usage: "total timeout for fetch",
EnvVar: "CONTAINERD_FETCH_TIMEOUT",
},
cli.StringFlag{
Name: "root",
Usage: "path to content store root",
Value: ".content", // TODO(stevvooe): for now, just use the PWD/.content
},
},
Action: func(context *cli.Context) error {
var (
// ctx = contextpkg.Background()
root = context.String("root")
)
if !filepath.IsAbs(root) {
var err error
root, err = filepath.Abs(root)
if err != nil {
return err
}
}
cs, err := content.Open(root)
if err != nil {
return err
}
active, err := cs.Active()
if err != nil {
return err
}
tw := tabwriter.NewWriter(os.Stdout, 1, 8, 1, '\t', 0)
fmt.Fprintf(tw, "REF\tSIZE\tAGE\n")
for _, active := range active {
fmt.Fprintf(tw, "%s\t%s\t%s\n",
active.Ref,
units.HumanSize(float64(active.Size)),
units.HumanDuration(time.Since(active.ModTime)))
}
tw.Flush()
return nil
},
}

72
cmd/dist/delete.go vendored Normal file
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@ -0,0 +1,72 @@
package main
import (
contextpkg "context"
"fmt"
"path/filepath"
"github.com/docker/containerd/content"
"github.com/docker/containerd/log"
digest "github.com/opencontainers/go-digest"
"github.com/urfave/cli"
)
var deleteCommand = cli.Command{
Name: "delete",
Aliases: []string{"del"},
Usage: "permanently delete one or more blobs.",
ArgsUsage: "[flags] [<digest>, ...]",
Description: `Delete one or more blobs permanently. Successfully deleted
blobs are printed to stdout.`,
Flags: []cli.Flag{
cli.StringFlag{
Name: "root",
Usage: "path to content store root",
Value: ".content", // TODO(stevvooe): for now, just use the PWD/.content
},
},
Action: func(context *cli.Context) error {
var (
ctx = contextpkg.Background()
root = context.String("root")
args = []string(context.Args())
exitError error
)
if !filepath.IsAbs(root) {
var err error
root, err = filepath.Abs(root)
if err != nil {
return err
}
}
cs, err := content.Open(root)
if err != nil {
return err
}
for _, arg := range args {
dgst, err := digest.Parse(arg)
if err != nil {
if exitError == nil {
exitError = err
}
log.G(ctx).WithError(err).Errorf("could not delete %v", dgst)
continue
}
if err := cs.Delete(dgst); err != nil {
if exitError == nil {
exitError = err
}
log.G(ctx).WithError(err).Errorf("could not delete %v", dgst)
continue
}
fmt.Println(dgst)
}
return exitError
},
}

96
cmd/dist/ingest.go vendored Normal file
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@ -0,0 +1,96 @@
package main
import (
contextpkg "context"
"fmt"
"os"
"path/filepath"
"strings"
"github.com/docker/containerd/content"
"github.com/opencontainers/go-digest"
"github.com/urfave/cli"
)
var ingestCommand = cli.Command{
Name: "ingest",
Usage: "accept content into the store",
ArgsUsage: "[flags] <key>",
Description: `Ingest objects into the local content store.`,
Flags: []cli.Flag{
cli.DurationFlag{
Name: "timeout",
Usage: "total timeout for fetch",
EnvVar: "CONTAINERD_FETCH_TIMEOUT",
},
cli.StringFlag{
Name: "path, p",
Usage: "path to content store",
Value: ".content", // TODO(stevvooe): for now, just use the PWD/.content
EnvVar: "CONTAINERD_DIST_CONTENT_STORE",
},
cli.Int64Flag{
Name: "expected-size",
Usage: "validate against provided size",
},
cli.StringFlag{
Name: "expected-digest",
Usage: "verify content against expected digest",
},
},
Action: func(context *cli.Context) error {
var (
ctx = contextpkg.Background()
timeout = context.Duration("timeout")
root = context.String("path")
ref = context.Args().First()
expectedSize = context.Int64("expected-size")
expectedDigest = digest.Digest(context.String("expected-digest"))
)
if timeout > 0 {
var cancel func()
ctx, cancel = contextpkg.WithTimeout(ctx, timeout)
defer cancel()
}
if err := expectedDigest.Validate(); expectedDigest != "" && err != nil {
return err
}
if !filepath.IsAbs(root) {
var err error
root, err = filepath.Abs(root)
if err != nil {
return err
}
}
cs, err := content.Open(root)
if err != nil {
return err
}
if expectedDigest != "" {
if ok, err := cs.Exists(expectedDigest); err != nil {
return err
} else if ok {
fmt.Fprintf(os.Stderr, "content with digest %v already exists\n", expectedDigest)
return nil
}
}
if ref == "" {
if expectedDigest == "" {
return fmt.Errorf("must specify a transaction reference or expected digest")
}
ref = strings.Replace(expectedDigest.String(), ":", "-", -1)
}
// TODO(stevvooe): Allow ingest to be reentrant. Currently, we expect
// all data to be written in a single invocation. Allow multiple writes
// to the same transaction key followed by a commit.
return content.WriteBlob(cs, os.Stdin, ref, expectedSize, expectedDigest)
},
}

85
cmd/dist/list.go vendored Normal file
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@ -0,0 +1,85 @@
package main
import (
contextpkg "context"
"fmt"
"os"
"path/filepath"
"text/tabwriter"
"time"
"github.com/docker/containerd/content"
"github.com/docker/containerd/log"
units "github.com/docker/go-units"
digest "github.com/opencontainers/go-digest"
"github.com/urfave/cli"
)
var listCommand = cli.Command{
Name: "list",
Aliases: []string{"ls"},
Usage: "list all blobs in the store.",
ArgsUsage: "[flags] [<prefix>, ...]",
Description: `List blobs in the content store.`,
Flags: []cli.Flag{
cli.StringFlag{
Name: "root",
Usage: "path to content store root",
Value: ".content", // TODO(stevvooe): for now, just use the PWD/.content
},
cli.BoolFlag{
Name: "quiet, q",
Usage: "print only the blob digest",
},
},
Action: func(context *cli.Context) error {
var (
ctx = contextpkg.Background()
root = context.String("root")
quiet = context.Bool("quiet")
args = []string(context.Args())
)
if !filepath.IsAbs(root) {
var err error
root, err = filepath.Abs(root)
if err != nil {
return err
}
}
cs, err := content.Open(root)
if err != nil {
return err
}
if len(args) > 0 {
// TODO(stevvooe): Implement selection of a few blobs. Not sure
// what kind of efficiency gains we can actually get here.
log.G(ctx).Warnf("args ignored; need to implement matchers")
}
var walkFn content.WalkFunc
if quiet {
walkFn = func(path string, fi os.FileInfo, dgst digest.Digest) error {
fmt.Println(dgst)
return nil
}
} else {
tw := tabwriter.NewWriter(os.Stdout, 1, 8, 1, '\t', 0)
defer tw.Flush()
fmt.Fprintf(tw, "DIGEST\tSIZE\tAGE\n")
walkFn = func(path string, fi os.FileInfo, dgst digest.Digest) error {
fmt.Fprintf(tw, "%s\t%s\t%s\n",
dgst,
units.HumanSize(float64(fi.Size())),
units.HumanDuration(time.Since(fi.ModTime())))
return nil
}
}
return cs.Walk(walkFn)
},
}

5
cmd/dist/main.go vendored
View file

@ -30,6 +30,11 @@ distribution tool
}
app.Commands = []cli.Command{
fetchCommand,
ingestCommand,
activeCommand,
pathCommand,
deleteCommand,
listCommand,
}
app.Before = func(context *cli.Context) error {
if context.GlobalBool("debug") {

89
cmd/dist/path.go vendored Normal file
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@ -0,0 +1,89 @@
package main
import (
contextpkg "context"
"fmt"
"path/filepath"
"github.com/docker/containerd/content"
"github.com/docker/containerd/log"
digest "github.com/opencontainers/go-digest"
"github.com/urfave/cli"
)
var pathCommand = cli.Command{
Name: "path",
Usage: "print the path to one or more blobs",
ArgsUsage: "[flags] [<digest>, ...]",
Description: `Display the paths to one or more blobs.
Output paths can be used to directly access blobs on disk.`,
Flags: []cli.Flag{
cli.StringFlag{
Name: "root",
Usage: "path to content store root",
Value: ".content", // TODO(stevvooe): for now, just use the PWD/.content
EnvVar: "CONTAINERD_DIST_CONTENT_STORE",
},
cli.BoolFlag{
Name: "quiet, q",
Usage: "elide digests in output",
},
},
Action: func(context *cli.Context) error {
var (
ctx = contextpkg.Background()
root = context.String("root")
args = []string(context.Args())
quiet = context.Bool("quiet")
exitError error
)
if !filepath.IsAbs(root) {
var err error
root, err = filepath.Abs(root)
if err != nil {
return err
}
}
cs, err := content.Open(root)
if err != nil {
return err
}
// TODO(stevvooe): Take the set of paths from stdin.
if len(args) < 1 {
return fmt.Errorf("please specify a blob digest")
}
for _, arg := range args {
dgst, err := digest.Parse(arg)
if err != nil {
log.G(ctx).WithError(err).Errorf("parsing %q as digest failed", arg)
if exitError == nil {
exitError = err
}
continue
}
p, err := cs.GetPath(dgst)
if err != nil {
log.G(ctx).WithError(err).Errorf("getting path for %q failed", dgst)
if exitError == nil {
exitError = err
}
continue
}
if !quiet {
fmt.Println(dgst, p)
} else {
fmt.Println(p)
}
}
return exitError
},
}

88
content/content.go
View file

@ -6,6 +6,7 @@ import (
"os"
"path/filepath"
"sync"
"time"
"github.com/docker/containerd/log"
"github.com/nightlyone/lockfile"
@ -45,9 +46,56 @@ func Open(root string) (*Store, error) {
type Status struct {
Ref string
Size int64
ModTime time.Time
Meta interface{}
}
func (cs *Store) Exists(dgst digest.Digest) (bool, error) {
if _, err := os.Stat(cs.blobPath(dgst)); err != nil {
if !os.IsNotExist(err) {
return false, err
}
return false, nil
}
return true, nil
}
func (cs *Store) GetPath(dgst digest.Digest) (string, error) {
p := cs.blobPath(dgst)
if _, err := os.Stat(p); err != nil {
if os.IsNotExist(err) {
return "", ErrBlobNotFound
}
return "", err
}
return p, nil
}
// Delete removes a blob by its digest.
//
// While this is safe to do concurrently, safe exist-removal logic must hold
// some global lock on the store.
func (cs *Store) Delete(dgst digest.Digest) error {
if err := os.RemoveAll(cs.blobPath(dgst)); err != nil {
if !os.IsNotExist(err) {
return err
}
return nil
}
return nil
}
func (cs *Store) blobPath(dgst digest.Digest) string {
return filepath.Join(cs.root, "blobs", dgst.Algorithm().String(), dgst.Hex())
}
// Stat returns the current status of a blob by the ingest ref.
func (cs *Store) Stat(ref string) (Status, error) {
dp := filepath.Join(cs.ingestRoot(ref), "data")
return cs.stat(dp)
@ -69,8 +117,8 @@ func (cs *Store) stat(ingestPath string) (Status, error) {
return Status{
Ref: ref,
Size: dfi.Size(),
ModTime: dfi.ModTime(),
}, nil
}
func (cs *Store) Active() ([]Status, error) {
@ -114,7 +162,14 @@ func (cs *Store) Active() ([]Status, error) {
// TODO(stevvooe): Allow querying the set of blobs in the blob store.
func (cs *Store) Walk(fn func(path string, dgst digest.Digest) error) error {
// WalkFunc defines the callback for a blob walk.
//
// TODO(stevvooe): Remove the file info. Just need size and modtime. Perhaps,
// not a huge deal, considering we have a path, but let's not just let this one
// go without scrunity.
type WalkFunc func(path string, fi os.FileInfo, dgst digest.Digest) error
func (cs *Store) Walk(fn WalkFunc) error {
root := filepath.Join(cs.root, "blobs")
var alg digest.Algorithm
return filepath.Walk(root, func(path string, fi os.FileInfo, err error) error {
@ -148,23 +203,10 @@ func (cs *Store) Walk(fn func(path string, dgst digest.Digest) error) error {
// store or extra paths not expected previously.
}
return fn(path, dgst)
return fn(path, fi, dgst)
})
}
func (cs *Store) GetPath(dgst digest.Digest) (string, error) {
p := filepath.Join(cs.root, "blobs", dgst.Algorithm().String(), dgst.Hex())
if _, err := os.Stat(p); err != nil {
if os.IsNotExist(err) {
return "", ErrBlobNotFound
}
return "", err
}
return p, nil
}
// Begin starts a new write transaction against the blob store.
//
// The argument `ref` is used to identify the transaction. It must be a valid
@ -267,6 +309,20 @@ func (cs *Store) Resume(ref string) (*Writer, error) {
}, nil
}
// Remove an active transaction keyed by ref.
func (cs *Store) Remove(ref string) error {
root := cs.ingestRoot(ref)
if err := os.RemoveAll(root); err != nil {
if os.IsNotExist(err) {
return nil
}
return err
}
return nil
}
func (cs *Store) ingestRoot(ref string) string {
dgst := digest.FromString(ref)
return filepath.Join(cs.root, "ingest", dgst.Hex())

11
content/content_test.go
View file

@ -14,6 +14,7 @@ import (
"reflect"
"runtime"
"testing"
"time"
"github.com/opencontainers/go-digest"
)
@ -59,6 +60,12 @@ func TestContentWriter(t *testing.T) {
t.Fatal(err)
}
// clear out the time and meta cause we don't care for this test
for i := range ingestions {
ingestions[i].Meta = nil
ingestions[i].ModTime = time.Time{}
}
if !reflect.DeepEqual(ingestions, []Status{
{
Ref: "myref",
@ -129,7 +136,7 @@ func TestWalkBlobs(t *testing.T) {
expected[dgst] = struct{}{}
}
if err := cs.Walk(func(path string, dgst digest.Digest) error {
if err := cs.Walk(func(path string, fi os.FileInfo, dgst digest.Digest) error {
found[dgst] = struct{}{}
if checked := checkBlobPath(t, cs, dgst); checked != path {
t.Fatalf("blob path did not match: %v != %v", path, checked)
@ -266,7 +273,7 @@ func checkBlobPath(t *testing.T, cs *Store, dgst digest.Digest) string {
}
func checkWrite(t checker, cs *Store, dgst digest.Digest, p []byte) digest.Digest {
if err := WriteBlob(cs, bytes.NewReader(p), int64(len(p)), dgst); err != nil {
if err := WriteBlob(cs, bytes.NewReader(p), dgst.String(), int64(len(p)), dgst); err != nil {
t.Fatal(err)
}

6
content/helpers.go
View file

@ -39,8 +39,8 @@ type Ingester interface {
// This is useful when the digest and size are known beforehand.
//
// Copy is buffered, so no need to wrap reader in buffered io.
func WriteBlob(cs Ingester, r io.Reader, size int64, expected digest.Digest) error {
cw, err := cs.Begin(expected.Hex())
func WriteBlob(cs Ingester, r io.Reader, ref string, size int64, expected digest.Digest) error {
cw, err := cs.Begin(ref)
if err != nil {
return err
}
@ -52,7 +52,7 @@ func WriteBlob(cs Ingester, r io.Reader, size int64, expected digest.Digest) err
return err
}
if nn != size {
if size > 0 && nn != size {
return errors.Errorf("failed size verification: %v != %v", nn, size)
}

38
content/writer.go
View file

@ -25,6 +25,21 @@ func (cw *Writer) Ref() string {
return cw.ref
}
// Size returns the current size written.
//
// Cannot be called concurrently with `Write`. If you need need concurrent
// status, query it with `Store.Stat`.
func (cw *Writer) Size() int64 {
return cw.offset
}
// Digest returns the current digest of the content, up to the current write.
//
// Cannot be called concurrently with `Write`.
func (cw *Writer) Digest() digest.Digest {
return cw.digester.Digest()
}
// Write p to the transaction.
//
// Note that writes are unbuffered to the backing file. When writing, it is
@ -32,6 +47,7 @@ func (cw *Writer) Ref() string {
func (cw *Writer) Write(p []byte) (n int, err error) {
n, err = cw.fp.Write(p)
cw.digester.Hash().Write(p[:n])
cw.offset += int64(len(p))
return n, err
}
@ -54,7 +70,7 @@ func (cw *Writer) Commit(size int64, expected digest.Digest) error {
return errors.Wrap(err, "failed to change ingest file permissions")
}
if size != fi.Size() {
if size > 0 && size != fi.Size() {
return errors.Errorf("failed size validation: %v != %v", fi.Size(), size)
}
@ -63,24 +79,23 @@ func (cw *Writer) Commit(size int64, expected digest.Digest) error {
}
dgst := cw.digester.Digest()
// TODO(stevvooe): Correctly handle missing expected digest or allow no
// expected digest at commit time.
if expected != "" && expected != dgst {
return errors.Errorf("unexpected digest: %v != %v", dgst, expected)
}
apath := filepath.Join(cw.cs.root, "blobs", dgst.Algorithm().String())
if err := os.MkdirAll(apath, 0755); err != nil {
var (
ingest = filepath.Join(cw.path, "data")
target = cw.cs.blobPath(dgst)
)
// make sure parent directories of blob exist
if err := os.MkdirAll(filepath.Dir(target), 0755); err != nil {
return err
}
var (
ingest = filepath.Join(cw.path, "data")
target = filepath.Join(apath, dgst.Hex())
)
// clean up!!
defer os.RemoveAll(cw.path)
if err := os.Rename(ingest, target); err != nil {
if os.IsExist(err) {
// collision with the target file!
@ -100,6 +115,9 @@ func (cw *Writer) Commit(size int64, expected digest.Digest) error {
// If one needs to resume the transaction, a new writer can be obtained from
// `ContentStore.Resume` using the same key. The write can then be continued
// from it was left off.
//
// To abandon a transaction completely, first call close then `Store.Remove` to
// clean up the associated resources.
func (cw *Writer) Close() (err error) {
if err := unlock(cw.lock); err != nil {
log.Printf("unlock failed: %v", err)